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Voltage drop

Shockwave said:
The fastest way to check if voltage drop is related to bad filter caps is to look at the output on a scope. Bad filter caps will place a lot of AC ripple on the carrier. You'll see the low frequency hum on the scope and hear it on the air.
Click to expand...

In any event the DC should never drop below the AC voltage by more than a few volts if it is caps and certainly never down to near zero as I believe was mentioned.
 
Good point CK, I missed the part about the voltage dropping to zero. Although, in a voltage doubler circuit it can drop well below what one might think since one bank of caps may not hold a charge and add voltage to the second bank. Then 50% of the DC will be gone but it should still not drop below the total RMS AC voltage applied to the rectifier. The caps just wont charge to the peak of the applied voltage.
 
Shockwave said:
Good point CK, I missed the part about the voltage dropping to zero. Although, in a voltage doubler circuit it can drop well below what one might think since one bank of caps may not hold a charge and add voltage to the second bank. Then 50% of the DC will be gone but it should still not drop below the total RMS AC voltage applied to the rectifier. The caps just wont charge to the peak of the applied voltage.
Click to expand...


Ed Zachery. :D
 
Crusher.

Measure the secondaries of the transformer under load. See if the voltage drop is at the transformer.
 
Just finished making cap bank and rectifier circuit/ doubler. Going to install tomorrow and see. If not, will measure V across output transformer. Have a fluke meter with HV probe that I can use. Rated for about 4kv AC.
 
Reason I was ask that the voltage be measured at the secondaries.

I have a tr here 2500vac secondary at 1.5 amp.

I can build a rectifier and cap filter circuit. Bring it up on a variac and it looks sweet on the HV meter.

Put that darn tr on an RF deck and the voltage goes to shit. the TR will not carry any current under load.
 
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wavrider said:
Reason I was ask that the voltage be measured at the secondaries.

I have a tr here 2500vac secondary at 1.5 amp.

I can build a rectifier and cap filter circuit. Bring it up on a variac and it looks sweet on the HV meter.

Put that darn tr on an RF deck and the voltage goes to shit. the TR will not carry any current under load.
Click to expand...


Have you checked for DC continuity thru the windings? I have seen some transformers that have such a high capacitance due to the high voltage windings that they will actually produce AC voltage on the secondary windings but only without a load. All it takes is a slight load to almost kill it.
 
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I will check first thing in morning. Now you have me wondering. Be a shame if that's the case. This is the big oversized transformer from peter dahl. Its double or possible tripple the size of original that came with amp.
 
When I get a chance to dig that heavy SOB out of the corner I will check it CK. Thanks.


Captain Kilowatt said:
Have you checked for DC continuity thru the windings? I have seen some transformers that have such a high capacitance due to the high voltage windings that they will actually produce AC voltage on the secondary windings but only without a load. All it takes is a slight load to almost kill it.
Click to expand...
 
Watch the meter as you hold the leads on it for several seconds. I have seen them look almost like an electrolytic capacitor. The meter jumps over to a low reading and tben slowly increases in resistance. Don't hold your fingers on the metal ends of the meter leads when you remove the leads from the windings or you will get a good understanding of what flyback is all about. :laugh:
 
CK: I thought "Like you" maybe one of the windings is breaking down under load.
This is where even a inexpensive transistor type "megger" is nice to have to check the primary/sec windings (both separately and together) to see if there is an internal breakdown...

Though I have the best success at work using a TTR (transformer/turns ratio)...but those ain't cheap!...
Though seems unlikely being it's a fairly new Peter Dahl xformer (even PD's are not made to abuse to that extent):blink:
All the Best
Gary
 

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